At present, more than about ten million optical recording disks, i.e., so-called CDs are produced monthly in Japan and a large amount of about ten and several tons of waste disks are produced monthly in Japan even by a small fraction defective. A present waste disk processing method that is employed by the waste disk processing specialists is that these waste disks are crushed and then buried. These waste disks are not recycled substantially.
The reason for this is that the optical recording disk has a multi-layer structure which comprises a base plate, a reflecting film such as Al evaporated film for reflecting a reproducing laser light, a protecting film formed thereon and a label printing film. Therefore, it is not possible to take out only the resin material from the waste disk. Consequently, the usage that the waste disk is recycled as a reclaimed plastic, i.e., reclaimed synthetic resin material is limited considerably.
Recently, from an environmental problem standpoint, the recycling of resin material is regarded as an important problem and several experiments are made in order to recycle the aforesaid optical recording disk. Under the present condition, there have been examined several methods of removing the Al evaporated film, the protecting film and the label film from the resin material. However, to realize these methods, an alkaline releasing liquid of high temperature and high concentration is required and such alkaline liquid is too dangerous. Also, there is then the problem that a secondary environmental pollution concerning the foul solution processing will occur.
Further, it is frequently observed that the waste disk is crushed as it is and then repelleted together with an enforcement. In this case, a material such as the Al evaporated film, the protecting film, the label printing film or the like is mixed into the pellet thus produced so that, when such pellet is recycled for a variety of products, the molding condition is fluctuated. Further, physical characteristics such as flexural strength, flexural rigidity or the like of the molded product become unstable. There is then the problem that the usage of such molded product is limited.
An optical recording disk material is excellent in flowability and transparent characteristic and has less optical distortion and contamination.
Accordingly, a polymer of low molecular weight and which has a small molecular weight distribution is utilized. This material is polycarbonate (PC), acrylic resin and amorphous polyolefin and optical materials of some special grades are now commercially available on the market. These materials are low in shock resistance and poor in mechanical characteristic as compared with a general molded grade material.
The material reclaimed from these disks is subjected to thermal hysteresis and is therefore made lower in shock resistance. Thus, the above material cannot be applied to function parts substantially.
For this reason, almost all of these materials are buried excepting that a spool and a runner are utilized as an extending agent of recycled PC by the reclaiming specialist.
On the other hand, CD cases that are formed by utilizing an optical recording disk recycled material are already commercially available on the market (see Japanese laid-open patent publication No. 4-253677). These cases have such features that aluminum pieces in the recording layer are properly dispersed to increase a design characteristic. However, since the mixed amount (the recording layer, the protecting layer and the label layer) of impurity material cannot be controlled. There is then the risk that a physical characteristic thereof is fluctuated. Thus, a field in which such recycled material is applied to the function molded product also is narrow.
An object of the present invention is to take out easily a base material of optical recording disk without impurity materials such as an Al (aluminum) evaporated film or the like so that a resin material can be recycled efficiently.
Another object of the present invention is to obtain from an optical recording disk a reclaimed resin material which can provide shock resistance sufficient so that various cases such as an accommodating case, i.e., CD case, a cabinet or the like can protect an accommodated product when applied as a recycled molded product of the optical recording disk or which can provide a mechanical strength sufficient that it is requested to have as a general molded product.